Recently, electronic devices have been developed that are able to track the movement of the electronic device by comparing images sampled by the electronic device at different points in time. For example, optical computer mice compare images of a surface that the mouse is moved over to determine motion of the optical mouse.
In one conventional system, the electronic device has a small light-emitting diode (LED) that emits light that reflects light off almost any surface and back to a complimentary metal oxide semiconductor (CMOS) sensor in the electronic device. This produces in a two-dimensional image of a portion of the surface. The CMOS sensor digitizes the two-dimensional image and sends each digitized image to a digital signal processor (DSP), which compares the current image with a previously captured reference image to determine the motion of the electronic device.
Such optical navigation has many advantages, among which are the lack of moving parts that accumulate dirt and suffer mechanical wear and tear of use. Another advantage of an optical mouse is that it does not need a mouse pad, since it is generally capable of navigating upon arbitrary surfaces, so long as they are not optically featureless. Optical navigation works quite well for a variety of surfaces. However, due to the nature of some surfaces, the electronic device tracks well when moved on some directions across the surface, but has difficulty tracking when moved in another direction across the surface.
As optical navigation is based on a comparison of images, repetitive features in a surface can make it difficult to properly compare the images. For example, some optical mice encounter difficulties when operating on some wood grained surfaces. Grainy surfaces may also present problems, depending upon feature size, as well as orientation.
Thus, one problem with conventional methods to detect motion using image processing methods is the difficulty in working with a wide spectrum of images. Another problem with conventional methods to detect motion using image processing methods is the difficulty in detecting motion with respect to some surfaces.